The blue shark (Prionace glauca) is one of the ocean’s most recognizable and wide-ranging pelagic shark species. Public interest in their status has grown significantly as media coverage continues to highlight the pressures facing global shark populations. The question of whether the blue shark is endangered is complex, requiring a look beyond a single global classification to understand the nuance of their conservation challenges.
Defining the Blue Shark
The blue shark is characterized by its long, slender body and brilliant indigo to deep blue coloring on its dorsal side. This species is an oceanic, epipelagic shark, meaning it lives in the open ocean, primarily in the upper water column down to about 600 meters. They possess a global distribution, inhabiting the temperate and tropical waters of all the world’s oceans, with the exception of the polar seas. Blue sharks are highly migratory, often undertaking transoceanic journeys following warm currents and reproductive cycles. They exhibit a relatively high reproductive rate compared to some other large sharks, giving birth to large litters that can average around 34 pups after a gestation period of nine to twelve months.
Global Conservation Status
The International Union for Conservation of Nature (IUCN) Red List currently classifies the blue shark’s global population as Near Threatened (NT). This classification indicates that the species does not yet qualify for the Vulnerable, Endangered, or Critically Endangered categories, but is likely to qualify for a threatened category in the near future. The global population is decreasing, with estimates suggesting a population reduction of 20–29% over the past three decades. The Near Threatened status, however, masks severe regional declines in specific areas. For instance, the blue shark population within the Mediterranean Sea is classified as Critically Endangered (CR). This extreme regional decline is attributed to high fishing pressure and the exploitation of immature individuals, which limits the population’s ability to reproduce and recover. The difference between the global and regional assessments highlights the challenge of managing a species with a vast, transboundary range.
Key Drivers of Population Decline
The primary threat to the blue shark population is commercial fishing, which captures millions of individuals annually. This species is one of the most frequently caught sharks in the world. Blue sharks are a common victim of bycatch in high-seas tuna and swordfish longline fisheries, which deploy thousands of baited hooks over many miles of ocean. Although historically considered bycatch, blue sharks are increasingly being retained by commercial fleets for their economic value. They are highly sought after for their fins, which are among the most heavily traded in the international market, and are also utilized in the global shark meat trade. Large-scale commercial longliners are responsible for approximately 90% of the blue shark catches, placing immense pressure on their populations.
International Management Efforts
Managing the blue shark is complicated because it crosses the jurisdiction of multiple nations and international waters. Regional Fisheries Management Organizations (RFMOs) are the main entities attempting to monitor and regulate the species. The International Commission for the Conservation of Atlantic Tunas (ICCAT), for example, conducts stock assessments for the Atlantic blue shark populations. Despite scientific recommendations for stricter measures, many RFMOs have not yet adopted specific catch limits for the blue shark. International agreements, such as the listing of the species on Appendix II of the Convention on International Trade in Endangered Species (CITES), aim to regulate the trade of their fins and meat to ensure it does not threaten the survival of wild populations.